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https://issues.apache.org/jira/browse/KAFKA-6555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ashish Surana updated KAFKA-6555:
---------------------------------
    Description: 
State store in Kafka streams are currently only queryable when StreamTask is in 
RUNNING state. The idea is to make it queryable even in the RESTORATION 
(PARTITION_ASSIGNED) state as the time spend on restoration can be huge and 
making the data inaccessible during this time could be downtime not suitable 
for many applications.

When the active partition goes down then one of the following occurs:
 # One of the standby replica partition gets promoted to active: Replica task 
has to restore the remaining state from the changelog topic before it can 
become RUNNING. The time taken for this depends on how much the replica is 
lagging behind. During this restoration time the state store for that partition 
is currently not queryable giving making the partition down. We can make the 
state store partition queryable for the data already present in the state store.
 # When there is no replica or standby task, then active task will be started 
in one of the existing node. That node has to build the entire state from the 
changelog topic which can take lot of time depending on how big is the 
changelog topic, and keeping state store not queryable during this time is the 
downtime for the parition.

It's very important improvement as it could simply improve the availability of 
microservices developed using kafka streams.

I am working on a patch for this change. Any feedback or comments are welcome.

 

 

  was:
State store in Kafka streams are currently only queryable when StreamTask is in 
RUNNING state. The idea is to make it queryable even in the RESTORATION 
(PARTITION_ASSIGNED) state as the time spend on restoration can be huge and 
making the data inaccessible during this time could be downtime not suitable 
for many applications.

When the active partition goes down then one of the following occurs:
 # One of the standby replica partition gets promoted to active: Replica task 
has to restore the remaining state from the changelog topic before it can 
become RUNNING. The time taken for this depends on how much the replica is 
lagging behind. During this restoration time the state store for that partition 
is currently not queryable giving making the partition down. We can make the 
state store partition queryable for the data already present in the state store.
 # When there is no replica or standby task, then active task will be started 
in one of the existing node. That node has to build the entire state from the 
changelog topic which can take lot of time depending on how big is the 
changelog topic, and keeping state store not queryable during this time is the 
downtime for the parition.

It's very important improvement as it could simply improve the availability of 
microservices developed using kafka streams. Any feedback or comments are 
welcome.

 

 


> Making state store queryable during restoration
> -----------------------------------------------
>
>                 Key: KAFKA-6555
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6555
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Ashish Surana
>            Priority: Major
>
> State store in Kafka streams are currently only queryable when StreamTask is 
> in RUNNING state. The idea is to make it queryable even in the RESTORATION 
> (PARTITION_ASSIGNED) state as the time spend on restoration can be huge and 
> making the data inaccessible during this time could be downtime not suitable 
> for many applications.
> When the active partition goes down then one of the following occurs:
>  # One of the standby replica partition gets promoted to active: Replica task 
> has to restore the remaining state from the changelog topic before it can 
> become RUNNING. The time taken for this depends on how much the replica is 
> lagging behind. During this restoration time the state store for that 
> partition is currently not queryable giving making the partition down. We can 
> make the state store partition queryable for the data already present in the 
> state store.
>  # When there is no replica or standby task, then active task will be started 
> in one of the existing node. That node has to build the entire state from the 
> changelog topic which can take lot of time depending on how big is the 
> changelog topic, and keeping state store not queryable during this time is 
> the downtime for the parition.
> It's very important improvement as it could simply improve the availability 
> of microservices developed using kafka streams.
> I am working on a patch for this change. Any feedback or comments are welcome.
>  
>  



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